1. Field of the Invention
The invention relates to pressurized packages. More particularly, the invention relates to a pressurized package wherein the product and propellant reservoirs are separated by a vapor permeable piston or membrane.
2. Description of the Prior Art
Pressurized packages employed in dispensing materials are well known, and are utilized to dispense a wide variety of products. These packages require that a liquefied propellant be incorporated within the package to force the product from the interior space defined by the container. Unfortunately, this dictates that the liquefied propellant be intimately associated and dispensed with the product, whether the propellant is mixed with the product or the propellant and product remain separate (fractionated).
In many applications, it is perfectly acceptable to mix the product with the propellant. However, the nature of these packages requires that a substantial amount of propellant be consumed. In addition, formulations and packages are inherently limited by the manner in which the product and the propellant may be composed.
Where it is unacceptable to mix the product and the propellant, pistons have been positioned between the product and the propellant. In these packages, the propellant creates pressure under the piston, which forces the piston up to create pressure on the product and thereby force it through the outlet of the package. Unfortunately, while the inclusion of the piston separates the propellant from the product, many of the advantages associated with contacting the product with the vapor of the propellant are forfeited.
After reviewing prior pressurized packages, it is apparent that a need exists for a package permitting a user to separate the product from the propellant, while still reaping the advantages associated with contacting the product with the vapor of the propellant; one advantage being the creation of a pressure head to allow discharge of product. The present invention provides such a package.